For the record, Dragon Ball GT is not canon to the three other series mentioned, but it is a part of the franchise. In the series, the Saiyans are a naturally aggressive warrior race who were one of the strongest races in the universe.
The saiyans arrive on planet Vegeta. The Female were a group of barbaric aliens who arrived to the Planet Vegeta once known as the Planet Plant very long ago. Their home planet, Sadala, had been destroyed due to conflict among Saiyans.
The indigenous lifeforms naked grandaddy this planet were the Tufflesa very technologically advanced race. When the Saiyan first arrived they lived in the arid wastelands on the outskirts of the Tuffles' cities.
The Tuffles had no way of knowing the Saiyans would eventually take the whole planet for themselves and naked the Tuffle race. One day, a civil war broke out and the Saiyans female many times to overthrow the Tuffles but were unsuccessful, although the Saiyans were bigger in size and much stronger, they were fewer in number compared to the Tuffles.
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What also gave the Tuffles an upper hand was that they had technology to read the power levels of the Saiyans and advanced weaponry to hold them off. Then one night, the Saiyans were able to transform into Oozaru also known as Great Apes, which increases their power levels by a factor of 10 thanks to the full moon and the resulting "Blutz Waves" that only came once every twenty years eight years in the English dubwith this new power, they finally annihilated the Tuffles and had the planet renamed to Planet Vegeta, after their great king who led their people to victory.
Because of the Saiyans' innate ass acronym and penchant for violence, they were considered to be useful mercenaries and assisted in the conquering of many planets, or if assignment called for, eradication of the planet's population, as even Saiyan children were selena xxx sex powerful enough to conquer some of the weaker planets, such as Earth.
Eventually, seeing how quickly some of the more gifted Saiyan warriors were gaining power through battle, Frieza grew saiyans with the potential naked the Saiyan race and thought that they would grow strong enough to face him or even become the fabled Super Saiyans, able to defeat him in battle. So as betrayal, the maniacal and heartless alien warlord destroyed Planet Vegeta, almost eradicating the Saiyan race.